MAWP Calculation

6.3.6 of what? Your specification?

They seem thought tobe referring to the same thing for most, but not all pumps.

SO max Diff pressure might not happen at zero flow, but if it did then its the same thing.

What does the definition section say?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

MAWP >= MAX Discharge Pressure + 10% Max differential pressure.

Since
Max Discharge Pressure = Max suction pressure + max Differential Pressure
Then
Max suction pressure + max Differential Pressure + 10% of max differential Pressure
Making your specified MAWP

MAWP >= Max suction pressure + max Differential Pressure + 10% of max differential Pressure

MAWP >= Max suction pressure + (1.1 * max Differential Pressure)

Maximum differential pressure occurs at the flow rate as seen on the pump curve.
Note that all pumps do not have their max dP at 0 flow, especially PD pumps.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

Assuming this is API 610 I think you've misunderstood table 16. That appears to list the acceptance criteria for testing the actual compared to the theoretical.

You should be using the actual if at all possible.

But this is only 10% tolerance so the 10% for MAWP is only 10% of that so only 1% in total.

Not going to be important.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.